Effect of extrusion and cold deformation on microstructure and mechanical properties of Al-Li/2024 heterostructured alloy

The powder metallurgy process is essential for designing aluminum-lithium alloy structures. However, research on the effects of the oxide layer on powder surfaces regarding the microstructure and properties of these alloys remains lacking. This study prepared an Al-Li/2024 heterostructure alloy using spark plasma sintering (SPS). The alloy was then subjected to T6 heat treatment, either after extrusion or after cold deformation. The resulting microstructural differences and mechanical properties were compared. The results indicate that the oxides exhibit a semi-continuous distribution after extrusion, which hinders the growth of recrystallized grains. Following cold deformation, the oxides become dispersed, leading to a loss of their inhibiting effect on recrystallization. Upon subjecting the materials to T6 heat treatment before and after cold deformation, it was observed that the yield strength decreased from 324.6 MPa to 237.1 MPa, while the tensile strength reduced from 413.0 MPa to 385.5 MPa. The elongation increased from 10.4% to 15.8%. The variations in material strength can be attributed to texture strengthening, dispersion strengthening, work hardening, and grain refinement strengthening. This article systematically investigates the influence of oxides on the microstructure and properties of aluminum-lithium alloys during deformation. It provides valuable references and guidance for the processing and heat treatment of powder metallurgy aluminum-lithium alloys.